Neurofibromatosis 1 is also known as von Recklinghausen disease, and it is caused by a mutation at chromosome 17q11.2. The protein normally expressed at this gene is believed to have the ability to suppress tumors, and maybe some other functions, too (this genetic stuff is still new to us, folks). The most common symptoms of NF1 look like the output of a random symptom generator:

People with NF1 can expect to live 10 to 15 years less than people without the disease. NF1 tends to form tumors on the nerves. NF type 1 affects some 1 in about 3000 births.

NF2 is located on the 22nd chromasome, and tends to form tumors in the brain, the central nervous system, and the spine. It is much rarer than NF1, occurring about once every 40,000 births. Symptoms include:

There is no cure for NF, but there are a few treatments that depend on symptoms. In some, symptoms are mild enough that they are essentially unaffected. For others, tumors are removed or killed as soon as they are spotted, and scoliosis is corrected with a back brace. There are no drugs on the market yet that treat NF.